Ar Gas Flow Research Articles

Controlled synthesis of large scale continuous monolayer WS2 film by atmospheric pressure chemical vapor deposition

Synthesis of monolayer transition metal dichalcogenides (TMDs) in large-size is crucial to their practical applications in electronics and optoelectronics. Here, large scale continuous monolayer WS2 film has been successfully grown by atmospheric pressure chemical vapor deposition (APCVD) method. By modulating three growth parameters, Ar gas flow rate, the temperature of WO3 precursor and the distance between substrate and WO3 precursor, WS2 film with different grain size can be obtained. At optimal processing condition, large-scale monolayer WS2 with lateral dimension can reach 1 mm above. This would pave the way for scale production of continuous monolayer TMDs film.

Factors Influencing Hardness of a Coating Material for Coating a Machine Component

This work investigated the influences of DC current, pressure and N2 to Ar gas flow rate on hardness of a TiN hard coating material for coating a fishing net-weaving machine component of a fishing net-weaving machine, namely upper hook. The target of this study was to maximize the hardness of TiN coated upper hook in order to maximize the corresponding wear resistance. Three process factors including DC current, operating pressure and N2 to Ar flow rate ratio were simultaneously investigated using the factorial design with replicates at the center point of the three factors method. Analysis of variance was used to investigate the effect of the three factors on the hardness of the TiN coated upper hook and the contour plots based on empirical model were plotted to obtain an appropriate operating condition of the statistically significant process factors with maximizing hardness value leading to the wear resistance of the upper hook. The results showed that the operating pressure and the N2 to Ar flow rate ratio and interaction among the three process factors significantly affected the average hardness at the level of significance of 0.05. Finally, an appropriate operating condition of the significant process factors was obtained at the higher levels of the operating pressure and the N2 to Ar flow rate ratio.

Efficient Nanostructured TiO2/SnS Heterojunction Solar Cells

AbstractTin sulfide (SnS) is one of the most promising solar cell materials, as it is abundant, environment friendly, available at low cost, and offers long‐term stability. However, the highest efficiency of the SnS solar cell reported so far remains at 4.36% even using the expensive atomic layer deposition process. This study reports on the fabrication of SnS solar cells by a solution process that employs rapid thermal treatment for few seconds under Ar gas flow after spin‐coating a precursor solution of SnCl2 and thiourea dissolved in dimethylformamide onto a nanostructured thin TiO2 electrode. The best‐performing cell exhibits power conversion efficiency (PCE) of 3.8% under 1 sun radiation conditions (AM1.5G). Moreover, secondary treatment using SnCl2 results in a significant improvement of 4.8% in PCE, which is one of the highest efficiencies among SnS‐based solar cells, especially with TiO2 electrodes. The thin film properties of SnS after SnCl2 secondary treatment are analyzed using grazing‐incidence wide‐angle X‐ray scattering, and high‐resolution transmittance electron microscopy.

Characterization Investigations of 2 wt% LaB6 Particulate-Reinforced Al-7 wt% Si Matrix Composites Fabricated by Powder Metallurgy Methods

In this study, first of all, sub-micron LaB6 reinforcing particles were synthesized in the size range of 100–500 nm via mechanochemical synthesis and leaching steps. Afterwards, Al-7 wt% Si matrix alloy and 2 wt% laboratory synthesized LaB6 powders were mechanically alloyed (MA’d) at different durations to constitute Al-7 wt% Si/2 wt% LaB6. Followed by compaction under a pressure of 450 MPa in a uniaxial cold press, samples were sintered at 570 °C for 2 h in flowing Ar gas atmosphere. Microstructural characterizations of the powders and sintered samples were performed using X-Ray Diffractometry (XRD) and Scanning Electron Microscopy (SEM) techniques. Effects of both MA (0, 1, 4 and 8 h) and LaB6 reinforcement (0 and 2 wt%) on the mechanical properties of the composites were determined in terms of microhardness and dry sliding tests. Both MA process and LaB6 reinforcement were found to make positive contribution to the hardness and wear resistance values. As-blended and sintered Al-7 wt% Si matrix alloy had a hardness value of 0.43 GPa. On the other hand, 8 h MA’d and sintered Al-7 wt% Si/2 wt% LaB6 composite had the highest hardness (0.97 GPa) and the 4 h MA’d one had the lowest wear rate (3.25 × 10−6 mm3/N mm) among all the sintered samples. The hardness and wear resistance values were increased by approximately 2 times in the 4 h MA’d and sintered Al-7 wt% Si-2 wt% LaB6 composite compared to its 1 h MA’d counterpart.

Characteristics of DLC/oxynitriding duplex-treated V8 tool steel by DC-pulsed PECVD

ABSTRACTIn this paper, DLC films are produced by DC-pulsed plasma enhanced CVD after oxynitride-treating of Vanadis 8 tool steel. The experimental parameters include various Ar gas flows (1, 1.5, 2 and 2.5 sccm) with asymmetric bipolar pulsed voltages, the gas flow of CH4 and a deposition time of 90 min, respectively. The experimental results showed that optimal properties occurred at an appropriate argon gas flow of 1.5 sccm. The wear tests showed the lowest wear loss volume when loads of 2 and 5 N were 3.81 × 10−3 and 4.01 × 10−3 mm3, respectively. Meanwhile, the hardness of the DLC film was 17.78 GPa and the elastic modulus was 191.63 GPa, respectively. Moreover, the water contact angle was 78.11°, which indicated that the DLC films could make Vanadis 8 tool steel more hydrophobic.

Rapid reaction sintering of silicon carbide using Nd:YAG laser

Reaction sintering of silicon carbide (SiC) using a continuous-wave Nd:YAG laser as a heating source was investigated. The laser was used to irradiate pellets of a stoichiometric powder mixture of Si and C under Ar gas flow. At an appropriate laser power, a dense SiC layer was formed consisting of grains with a size of 100–500 nm; this layer was several micrometers thick. At lower laser power, fine grains of SiC were formed and dispersed in the unreacted Si–C matrix. On the other hand, at higher power, larger faceted SiC grains (1–3 µm) were formed.

Effects of different milling conditions on the properties of lanthanum hexaboride nanoparticles and their sintered bodies

In this study, the preparation and consolidation of nanocrystalline LaB 6 powders originating from powder blends of La 2 O 3 , B 2 O 3 and Mg were reported. A consecutive route of mechanochemical synthesis (MCS) and purification was utilized for the achievement of nano-sized LaB 6 powders. As-synthesized powders were leached out from intermediate reaction products or impurities. Then, a sequential step of cold pressing (uniaxial pressure at 800 MPa) and pressureless sintering (at 1700 °C for 5 h under Ar gas flow) were utilized for the consolidation of the purified LaB 6 powders. The type of mill (vibratory and planetary high-energy ball mills) was employed as a MCS parameter to reveal its effect on the physical, microstructural and mechanical properties of the LaB 6 powders, and their bulk structures. Compositional, physical and microstructural properties of the products after powder processing were determined via X-ray diffractometer (XRD), particle size analyzer (PSA), differential scanning calorimeter (DSC), stereomicroscope (SM), scanning electron microscope (SEM), transmission electron microscope (TEM), energy dispersive spectrometer (EDS) coupled with both SEM and TEM, and vibrating sample magnetometer (VSM). The bulk properties of the LaB 6 consolidated from nanocrystalline powders with a minimum 99.99% purity, and ∼62 nm (for vibratory ball mill) or ∼74 nm (for planetary ball mill) average particle size were compared according to various properties. LaB 6 powders were synthesized in planetary mill at an approximately six times longer duration than that of in vibratory mill. According to the results, density, surface area and mean particle size values of the vibratory ball-milled samples (containing paramagnetic powders) are better than those of planetary ball-milled (containing diamagnetic powders) ones. However, mechanical properties such as hardness, surface roughness, wear rate, friction coefficient, and also electrical conductivity were improved in the planetary ball-milled LaB 6 bulks.

Mechanism and optimization of non-thermal plasma-activated water for bacterial inactivation by underwater plasma jet and delivery of reactive species underwater by cylindrical DBD plasma

Plasma-activated water (PAW) has been in use for the past decade in sanitization against bacteria and other microorganisms. This research study compared PAW generated by a DC positive flyback transformer (FBT) underwater plasma jet with delivery of reactive species underwater by cylindrical dielectric barrier discharge (C-DBD) with a neon transformer. A Box–Behnken design was adopted as a response surface methodology (RSM) to design the experimental plan and optimize operating parameters including time, gas flow, and gas ratio. The physical responses comprise optical emission spectroscopy (OES), pH, oxidation-reduction potential (ORP), and electrical conductivity (EC). The chemical responses consist of hydrogen peroxide (H2O2) and hydroxyl radicals (OH·). The biological responses include Escherichia coli reduction and Staphylococcus aureus reduction. The optimal condition for underwater plasma jet was found to be Ar gas with a flow rate of 3 slm for 6.5 min of treatment time, which can reduce E. coli and S. aureus to 7.14 ± 0.14 and 3.10 ± 0.26 in log, respectively. Also, the optimal condition for delivery of reactive species underwater by C-DBD plasma was found to be Ar (99%): O2 (1%) gas mixture with an Ar gas flow rate of 4 slm for a treatment time of 11.5 min, which could reduce E. coli and S. aureus to 0.45 ± 0.07 and 2.45 ± 0.23 in log, respectively.

Deoxidation of Ti Melt by Newly Developed Two-Step Plasma Arc Melting Process Using Hydrogen

A two-step plasma arc melting process, comprising a first step under Ar-30 pct H2 gas flow and the second step under Ar gas flow, has been newly developed for the deoxidation of Ti melts. The oxygen content after this process depended on the depth probed in the Ti melt. Decrease in the oxygen content from 1.5 to 0.7 mass pct in the surface region of the Ti melt occurred in the second step.

Temperature induced surface plasmon resonance in Au/a-C nanocomposite thin film

Nanocomposite thin film containing Au nanoparticles in carbon matrix is developed using co-sputtering method in a high vacuum chamber (<10−6 torr). The atomic concentration of Au metal (6 at. %) is kept low so that the properties of matrix are not deteriorated much by the presence of metal. In order to enhance the growth of Au nanoparticles to an appreciable size, thermal annealing is performed on the as-deposited films at increasing temperatures from 100 to 500 °C in an inert atmosphere (continuous flow of Ar gas is maintained during heating and cooling). Annealing is performed for 1 hr on each sample. Growth of the Au nanoparticles and evolution of carbon matrix by thermal treatment is understood through TEM and Raman spectroscopy. TEM images of the as-deposited sample taken at different areas of the sample clearly indicate the spherical-shaped Au nanoparticles with an average diameter of ∼1.5 nm which is further increased up to ∼15.3 nm at the temperature of 500 °C. The results of Raman spectroscopy confirm the increase in the intensity of characteristic D and G bands of amorphous carbon with temperature. Surface plasmon resonance is successfully induced by temperature treatment at a wavelength of ∼548 nm at 400 °C, which is further enhanced at 500 °C. The growth of Au nanoparticles is also confirmed by X-ray diffraction study.

Fundamental study on the vaporization of cesium and iodine dissolved in LiF-NaF-KF molten salt

As a basic study related to a severe accident of Molten Salt Reactor (MSR), the equilibrium vapor pressures over LiF-NaF-KF eutectic salt (46.5–11.5–42.0 mol%, FLiNaK) containing Cs and I as volatile Fission Product(FP) were measured by a transpiration method under pure Ar gas flow at the temperature ranging from 900 to 1100 K. As the result, the vapor pressures of Cs and I in molten FLiNaK were evaluated to be higher than those of other elements in the salt, and the vapor pressure of the solvent salt elements such as Li and K also increased with addition of CsI and CsF. The activity coefficients of CsI and CsF were derived from the partial vapor pressure of CsI and CsF calculated by assuming the gas phase equilibrium. Activity coefficients of CsI, 6 to 13 in this temperature range, showed strongly positive deviation from ideal solution while those of CsF were around unity. This peculiar activity coefficients suggest instability of CsI in the FLiNaK salt as suggested for LiF-ThF4-CsI salt by literature. The vaporization behaviors measured for the FLiNaK with different Cs/I ratio indicated strong interaction between Cs and I in FLiNaK salt.

Quadrupole ICPMS Determination of Iron in Drosophila melanogaster S2 Cell Cultures using Collision Cell and Desolvation Strategies

Inductively coupled plasma mass spectrometry (ICPMS) has become the preferred technique for trace and ultra‐trace determination of elemental concentrations in a wide variety of sample matrices. In our studies of iron uptake and metabolism in insect cells, we evaluated different ICPMS procedures to measure picogram to microgram quantities of iron in whole insects and Drosophila melanogaster S2 cells. While a well‐known spectrophotometric iron assay with ferrozine suffices for microgram amounts of the elements, ICPMS is imperative for lower level work.The determination of iron by ICPMS faces several significant challenges: samples must be decomposed to mineralize organic matter; the separation of iron from the matrix may be required in some circumstances; all sample preparation and analytical processes must be conducted under sufficiently “clean”, low‐blank conditions; and the interference of polyatomic ions (ArN+, ArO+, ArOH+) upon iron ions must be addressed. To address these challenges, samples were digested and mineralized by heating with nitric acid at 90°C in fluoropolymer containers. “Trace metal” grades of HNO3 were found to be satisfactory for minimizing reagent contributions to the overall blank. As quadrupole mass analyzers cannot distinguish between ions of the same nominal mass (e.g., 40Ar16O+ vs. 56Fe+), alternative strategies must be used to suppress the formation of polyatomic ions so that Fe+ ions can be observed above background signal. We used two different approaches. The first is de‐solvation of the sample aerosol, where water vapor is removed by a membrane dryer with countercurrent Ar gas flow. The second is passage of the extracted ions through a “collision cell” prior to mass analysis, which selectively attenuates the polyatomic ions via ion kinetic energy discrimination. A combination of both approaches lowered solution detection limits for Fe from ~ 50 – 100 micrograms/liter to &lt;&lt; 1 microgram/liter. We present optimized procedures for the routine determination of Fe in digested cell and insect tissue samples.Support or Funding InformationNSF IOS‐1656407This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Polymer-derived porous SiOC ceramic membranes for efficient oil-water separation and membrane distillation

Porous SiOC ceramic membranes (PSCM), with a narrow pore size distribution, were prepared by a casting method, using a polymer liquid (polydimethylsiloxane, PDMS), as a pore-forming agent, and a pre-ceramic liquid (polysiloxane, PSO), followed by pyrolysis at 1200 °C in flowing Ar gas. Pore size, porosity, and N2 and water permeation increased with increasing PDMS content in the mixture of the precursors. An oil-in-water emulsion, with an average oil diameter of 0.83 μm, was effectively separated (95% rejection rate) with membranes which had an average pore size of 0.59 μm. PDMS was also used for membrane surface modification and the surfaces became super-hydrophobic. After modification, membranes with an average pore size of 0.95 μm were tested in sweeping gas membrane distillation. High salt rejection of 99.9% was achieved with NaCl solution (at various concentrations, 4–16 wt%) at several temperatures (55–85 °C). A stable performance was recorded for over 100 h, using 4 wt% NaCl in the feed at 75 °C. The produced membranes displayed clear separation and high efficiency in separation rates, which was reflected in the high permeation flux in both oil-in-water emulsion filtration and membrane distillation, attributed to the narrow pore size distribution.

Controllable growth of vertical ReS2 nanosheets and nanorods by vapor transport method

As an emerging two-dimensional transition metal dichalcogenide, rhenium disulfide (ReS2) has been attracting more and more attention for its unique properties and great potential in the design of the electronic and optoelectronic devices. Here, for the first time, large-size ReS2 nanosheets with area of over 35 μm × 20 μm were successfully synthesized via vapor transport (VT) method. Moreover, the growth of ReS2 nanosheets via VT method was demonstrated to be effective on Si, SiO2, and Au substrate, which would further expand the application of ReS2 during the design of devices on different substrates. Besides, the effect of Ar gas flow on the growth of ReS2 nanosheets was systematically investigated. Furthermore, it is the first time the 1D ReS2 nanorods have been synthesized using the VT method. Based on the experiment results, the growth mechanism of ReS2 nanosheets and nanorods was proposed. It is believed that the research may pave a way for the growth of large-size ReS2 nanosheets and the wider application of ReS2 nanostructures.

Effect of cold atmospheric pressure plasma on DNA integrity in patients with asthenospermia

In this paper, we focused on the possible biomedical applications of the atmospheric pressure plasma, where we used plasma ignited in Argon (Ar) gas flow to study the effects of cold plasma on DNA integrity. Atmospheric pressure plasma, by needle, contains almost of equal amounts of positive and negative charges and has much potential for medical applications. A prospective study carried on 60 samples of human semen; each sample divided into 2 parts, before and after exposure to plasma, and then study the DNA integrity in both parts. Sperm DNA integrity was determined using a modified alkaline single cell gel electrophoresis (comet assay) and acridine orange test (AOT). The results showed that atmospheric pressure plasma give a significant (P< 0.05) decreasing in DNA damage for prepared sperm. Plasma for sperm preparation, decreases DNA damage.

Mathematical model for decarburization of ultra-low carbon steel during RH treatment

ABSTRACT A mathematical model was established to investigate the decarburization behaviour of ultra-low carbon steel during Ruhrstahl-Heraeus (RH) refining process. In this model, it was assumed that the decarburization reactions occur at four sites: Ar bubble surface, bath surface, bulk steel and splash droplet surface. The effect of Ar bubble behaviour and splash droplet behaviour on decarburization rate was taken into consideration specifically. The calculated results are basically consistent with the industrial experimental observations. Carbon concentration was mainly eliminated at bath surface at early stage of RH treatment, and was mostly removed in bulk steel at middle stage, and was removed at splash droplet surface in the final stage. The decarburization rate at different sites and its contribution to total decarburization value were evaluated in detail. The decarburization rate during RH treatment could be effectively improved by accelerating the drop of vacuum pressure at early stage. Appropriate increasing Ar gas flow rate was beneficial to deep decarburization by increasing the reaction area of droplet surface and bath surface.

Effect of plasma jet on the water and hydrogen peroxide that used for assisted teeth bleaching

In this work the interaction of plasma jet with water and hydrogen peroxide liquids used for assisted teeth bleaching by plasma jet had been study. A homemade plasma jet system was used. The plasma jet supply by 15 W electrical power generated by high voltage power supply of 9.6 kV peak to peak and frequency of 33 kHz .this power supply generate high electric field on electrodes that would be enough to ionize the argon gas. Some important agents were study such as the effect of the Ar gas flow rates on the length of the plasma jet, the influence of plasma jet on some properties of water and two hydrogen peroxide concentrations 25 % and 30 % like pH, conductivity and liquid temperature for different exposure time. The liquids temperature was measured by digital infrared thermometer, the gas flow rate were measured by gas flow meter, the pH, and the conductivity was measured by pH conductivity ultra-meter. The results illustrated that the conductivity and liquid temperature increase with increasing of exposure time. It can be conclude that the liquid properties were changed less than the boundaries that could affect adversely to the cells that located in the plasma jet.

Fabrication of a p-type Cu2O thin-film via UV-irradiation of a patternable molecular-precursor film containing Cu(II) complexes

A patterned p-type Cu2O thin-film was fabricated using 4-mW cm−2 ultraviolet (UV) irradiation onto a preheated precursor-film formed on a Na-free glass by spin-coating a solution containing Cu(II) complexes of propylamine and ethylenediamine, and post-annealing. After a small Na-free glass plate was placed on the spin-coated and preheated precursor-film to provide a UV-shielded area, the film was UV-irradiated for 6 h at room temperature. X-ray diffraction measurement indicated that the UV-irradiation converted the Cu(II) complexes to crystallized Cu2O. The patterned film obtained by removal of the UV-shielded portion with immersion into water was then post-annealed at 400 °C for 3 min in an Ar-gas flow. The Hall effect measurement of the resultant film of a 90 nm thickness showed that the electrical resistivity, carrier concentration, and hole mobility were 1.4(2) × 102 Ω cm, 8(3) × 1016 cm−3, and 0.9(3) cm2 V−1 s−1, respectively.

Deposition of ZrON thin films by reactive magnetron sputtering using a hollow cylindrical target

ZrON films were prepared on quartz glass and glassy carbon substrates by reactive sputtering using a hollow cylindrical cathode with a Zr target. In the cathode cylinder, the plasma density increased with increasing lateral distance from the axial center of the cylinder, whereas it decreased with increasing lateral distance from the cylinder. The damage to the substrates during film deposition was evaluated by the transmission spectra of Rhodamine B films before and after sputtering. The film deposition was performed in Ar and N2 gas flows with various O2 flow rates while heating the substrates with a ceramic heater. Scanning electron microscope observation indicated homogeneous thickness of the films. X-ray diffraction measurement showed that the ZrON films were a mixture of crystalline ZrN, Zr2ON2, Zr7O8N4, and ZrO2 phases. The fractions of these crystalline phases in the films depended on the O2 flow rate. X-ray photoemission spectroscopy measurement and its analysis revealed that the binding energy of the Zr 3d doublet corresponding to precipitated ZrON crystals in the films, such as Zr2ON2 and Zr7O8N4, increased with increasing oxygen flow rate. Electrochemical measurement revealed that the film deposited at an O2 flow rate of 0.6 sccm had the largest redox potential of 0.51 V (vs standard hydrogen electrode, −5 μA/cm2). The Zr7O8N4 crystals precipitated in the film play a key role in achieving the high redox potential.

Highly-Conductive and Well-Adhered Cu Thin Film Fabricated on Quartz Glass by Heat Treatment of a Precursor Film Obtained Via Spray-Coating of an Aqueous Solution Involving Cu(II) Complexes

A Cu thin film on a quartz glass substrate was fabricated by a wet process involving heat-treatment of a precursor film spray-coated with an aqueous ammonia solution containing Cu(HCOO)2∙4H2O and Cu(II) complex of ethylenediamine-N,N,N′N′-tetraacetic acid. The precursor film that formed on the substrate at 180 °C in air was heat-treated at 350 °C and post annealed at 400 °C by placing an identical-sized glass on top, under Ar gas flow in a tubular furnace. X-ray diffraction pattern of the resultant film showed only peaks of Cu. The resultant film of 100 nm thickness has an adhesion strength and electrical resistivity of 37(7) MPa and 3.8(6) × 10−5 Ω cm, respectively. The images of atomic force and field-emission scanning-electron microscopies revealed a film of well-connected Cu grains with an average surface roughness of 11 nm. The reflectance of the thin film is more than 90% in the far-infrared region. The film’s chemical composition was also examined by using Auger electron spectroscopy.